Geology topics

K. Meyer

Publications and source records attributed to K. Meyer.

5 recordsLinked to original sources

USGS2019

Potential threats facing a globally important population of the magnificent frigatebird Fregata magnificens

Tracking of seabirds has been used to identify foraging hotspots, migratory routes and to assess at-sea threats facing populations. One such threat is the potential negative interaction between seabirds and fisheries through incidental by-catch. In 2012, 60 magnificent frigatebirds Fregata magnificens were found dead, entangled in fishing line, at the globally important breeding site in the British Virgin Islands (BVI). To assess the potential relationship between foraging behaviour and fishing activity, data loggers were deployed on breeding magnificent frigatebirds to record foraging movements. In addition, a survey of local fishers was conducted to assess the scale of incidental by-catch. We recorded 28 complete foraging trips from GPS and GPS-GSM loggers, and 1758 PTT locations. Birds travelled up to 3.3–1067 km from their breeding colony and entered the waters of 10 neighbouring territories. A high percentage of fishers (93% n = 28) reported catching at least one seabird annually, of which the most common were magnificent frigatebirds and brown boobies Sula leucogaster . There are estimated to be at least 1112 vessels in the recreational and artisanal fishing fleets of BVI and its neighbouring islands. Thus, this substantial fishery may have potentially profound effects on seabird populations in the region.

Tropical Zoology↗

USGS2016

10,000 m under the sea: An overview of the HADES expedition to Kermadec Trench

The hadal zone of the world oceans (6000– 11,000 m) occupies <1% of the marine realm and is found almost exclusively in trenches but represents ~40% of the total ocean depth range. Jamison et al. (2010 & Jamison, 2015) have reviewed the current state of knowledge about the hydrology, physical characteristics, food supply, ecology and biodiversity of life in hadal trenches. This review concluded that, there appears to be a high level of endemism based on the few specimens collected from historical sampling efforts in the 1950s (Danish Galathea and Soviet Vitjaz expeditions), but because trenches are still largely unexplored there is a lot we do not know about the ecological structure and functioning of hadal environments. However, relatively recent advances in technology using remotely operated vehicles (ROV) and landers can help us explore hadal trenches in greater detail.

Conference Paper↗

USGS2006

The western pond turtle (Clemmys marmorata) in the Mojave River, California, USA: Highly adapted survivor or tenuous relict?

Aspects of the ecology of populations of the western pond turtle Clemmys marmorata were investigated in the Mojave River of the central Mojave Desert, California, U.S.A. One population occupied man-made ponds and the other occurred in natural ponds in the flood plain of the Mojave River. Both habitats are severely degraded as a result of ground water depletion from human activities along the river and one is infested with the exotic shrub saltcedar Tamarix ramosissima . Mean female carapace length (CL) was significantly greater (14.4 cm) than that of males (13.7 cm). Live juveniles were not detected during the period of study. Shelled eggs were visible in X-radiographs from 26 May to 14 July. Mean clutch size was 4.46 and ranged from 3 to 6 eggs. Clutch size did not vary between 1998 and 1999 but was significantly correlated with CL for both years combined, increasing at the rate of 0.548 eggs/cm CL. Gravid female CL ranged from 13.3–16.0 cm. Some females nested in both years. Mean X-ray egg width (21.8 mm) was not significantly correlated with CL or clutch size. X-ray egg width differed more among clutches than within, whether including CL as a co-variate or not. Nesting migrations occurred from 6 June to 8 July with minimum round trip distances ranging from 17.5–585 m with a mean of 195 m. Mean estimated time of departure as measured at the drift fence was 18:13. Most females returned to the ponds in the early morning. Nesting migrations required females to be out of the water for estimated periods of 0.83 to 86 h. The destination of nesting females was typically fluvial sand bars in the channel of the dry riverbed. Overall, the ecology of C. marmorata in the Mojave River is very similar to that reported for populations in less severe habitats along the west coast of the United States. Notable exceptions include long nesting migrations to sandbars in the dry river channel, a possible result of human modifications to the environment, and an apparent lack of terrestrial overwintering behaviour in Mojave River populations. The general similarity of desert and coastal populations is possibly a reflection of their recent geographic separation. Overall, populations in the Mojave River exhibit few obvious adaptations to living in the desert and are considered to be tenuous relicts of the Pleistocene. The small size and tenuous status of these populations suggests that immediate conservation action is needed, including establishment of satellite populations as a hedge against extirpation.

California↗

USGS2004

Roosevelt elk density and social segregation: Foraging behavior and females avoiding larger groups of males

Intersexual social segregation at small spatial scales is prevalent in ruminants that are sexually dimorphic in body size. Explaining social segregation, however, from hypotheses of how intersexual size differences affects the foraging process of males and females has had mixed results. We studied whether body size influences on forage behavior, intersexual social incompatibility or both might influence social segregation in a population of Roosevelt elk ( Cervus elaphus roosevelt ) that declined 40% over 5 y. Most males and females in the population occurred in the same forage patches, meadows, but occupied different parts of meadows and most groups were overwhelming comprised of one sex. The extent of segregation varied slightly with changing elk density. Cropping rate, our surrogate of forage ingestion, of males in mixed-sex groups differed from males in male-only groups at high, but not low, elk density. In a prior study of intersexual social interactions it was shown that females avoided groups containing ≥6 males. Therefore, we predicted that females should avoid parts of meadows where groups of males ≥6 were prevalent. Across the 5 y of study this prediction held because ≤ 5% of all females were found in parts of meadows where median aggregation sizes of males were ≤ 6. Social segregation was coupled to body size influences on forage ingestion at high density and social incompatibility was coupled to social segregation regardless of elk density.

American Midland Naturalist↗

USGS1999

Studies of reproductive output of the desert tortoise at Joshua Tree National Park, the Mojave National Preserve, and comparative sites

The stability of any population is a function of how many young are produced and how many survive to reproduce. Populations with low reproductive output and high mortality will decline until such time as deaths and births are at least balanced. Monitoring populations of sensitive species is particularly important to ensure that conditions do not favor decline or extinction. Turtles, including tortoises, are characterized by life history traits that make them slow to adapt to rapid changes in mortality and habitat alteration. Long life spans (in excess of 50 years), late maturity, and widely variable nest success are traits that allowed turtles to outlive the dinosaurs, but they are poorly adapted for life in the rapidly changing modern world. Increased mortality of young and adults can seriously tip the delicate balance required for turtles to survive.

Park Science↗